The present invention generally relates to a selective catalytic reduction (SCR) device for converting NOx in the gas stream into H2O and N2. More particularly, the present invention is directed to a catalyst loading device for loading and unloading catalyst blocks in an SCR device, and methods therefor.
SCR devices using catalyst blocks are often used in applications where NOx removal from flue gases is needed. In such cases, the SCR catalyst blocks are placed within the SCR reactor through which the combustion flue gases are conveyed. FIG. 1 shows a perspective view of an SCR reactor box (or SCR device) with fully and partially loaded catalyst block sections. There is an entrance for the catalyst loading device to enter for loading and unloading the catalyst blocks. The entrance and height between layers of catalyst is such that it allows enough space for the catalyst loading device (with or without a catalyst block) and the operator to enter the SCR device for loading and unloading the catalyst blocks. As shown in FIG. 1, the height between layers of catalyst layers is very limited, ranging anywhere from 10 to 12 feet high. As the available space between the top of the catalyst block and overhead obstructions (e.g., piping, sonic horns, sootblowers, etc.) is minimal, there is only room for the catalyst loading device structure, and no room for lifting machinery.
In order to remain effective, the catalyst should be protected from accumulation of particulate contaminants, which may deposit on the catalyst or otherwise restrict gas flow to and/or through the catalyst. Also catalyst is deactivated over time by the NOx removal process. In either case, removal and replacement or reloading of a catalyst block may be periodically required.
Existing industry solutions include a commercial walk behind fork lift on heavy duty pertinent grating, expanding hydraulic carts running on a secondary grid below the catalyst blocks, or multiple overhead trolley beam and hoists.
Typically, catalyst loading devices used in the industry run on the lower flanges of the overhead catalyst structural support frame or dedicated overhead trolley beams. This means that the shapes of the catalyst supporting beams are typically constructed of overhead trolley beams with flanges. These flanges continue to be a problem since they can collect ash which can fall off and are a starting place for catalyst pluggage.
Catalyst loading device structural support frames that require lifting from underneath the catalyst blocks continue to be a problem since they must be wider than the catalyst blocks, requiring extra space on one side of the block for the structural support frame and lifting mechanism, which also increases the overall width of the catalyst reactor box.
One method of loading and unloading catalyst blocks in a SCR device typically uses walk behind forklifts to move the catalyst blocks into the approximate location and then moves them into final placement with pry bars, which may increase the chance of personal injury.
United States Patent Application Publication Number US 2014/0227073 to Nelson et al. is drawn to an overhead catalyst loading device that eliminates the need for lower flanges of the overhead catalyst structural support frame or dedicated overhead trolley beams to prevent ash build up collecting on a SCR reactor box and provides an advantageous lifting mechanism suitable for integration into a SCR device. Nelson et al. uses a hydraulic pump to provide pressure to a lifting mechanism to engage a lifting frame of a lifting structure, and the force exerted by the lifting mechanism is transmitted into the lifting structure, causing it to be displaced vertically, thereby lifting the catalyst block coupled thereto. See FIGS. 2 and 3 for drawings of the prior art catalyst loading device.
It would be desirable to provide a catalyst loading device that eliminates the need for overhead trolley beams with ledges in the form of the support beam flanges to prevent ash build up collecting on the SCR reactor box and provides an advantageous electric hydraulic lifting mechanism suitable for integration into the SCR unit that minimizes the chance of injury, lessens the exertion of operator energy, and increases the speed and rate of loading and unloading catalyst blocks in the SCR device, which remains of significant commercial interest in the industry.